1. Field of the Invention
The present invention relates to an exposure apparatus and a method of manufacturing a device such as a color filter or a liquid crystal display device using the exposure apparatus.
2. Description of the Related Art
A variety of methods of manufacturing color filters have been developed, and include, for example, staining methods, printing methods, electrodeposition and electrolytic methods, and pigment dispersing methods. Among such of methods, the pigment dispersing methods are the current mainstream from the viewpoint that they are stable and easy manufacture. A method of using a photosensitive acrylic polymer as a typical pigment dispersing method forms a pattern on a color resist, which contains an acryloid photosensitive resin and has both a coloring function and a photosensitizing function, using a photolithography technique. This color resist is a negative resist, and produces radicals, which contribute to a polymerization reaction, upon being irradiated with light for use in exposure, forms polymers by photopolymerization, and becomes insoluble in a developer. However, this color resist is hindered from bringing about the polymerization reaction because its pigment components easily absorb the exposure light, and the radicals produced by it are trapped by oxygen in the air. Hence, to obtain a desired pattern shape, exposure light with a higher energy must be used. To avoid this, a known method provides an oxygen barrier film, which is made of polyvinyl alcohol and blocks off oxygen, on the resist. However, this method may generate defects because the oxygen barrier film has poor wettability on the resist, and requires a higher cost related to an additional process of coating a resist with an oxygen barrier film. Furthermore, in the method of providing an oxygen barrier film, the oxygen concentration cannot be controlled, and this lowers the flexibility for finer pattern shape/dimensional precision control in forming a fine pattern.
To solve these problems of the method of providing an oxygen barrier film, Japanese Patent Laid-Open No. 1-195445, for example, proposes a method of exposing a resist film under a low-oxygen concentration condition by blowing nitrogen gas onto it without providing a polyvinyl alcohol film on it.
In a step which requires exposure under a low-oxygen concentration condition to decrease the exposure dose in a process of manufacturing, for example, a color filter, it is a common practice to expose a resist by blowing an inert gas such as nitrogen onto the resist. However, a performance problem is posed when the inert gas is always blown onto the resist to purge it. In a step which does not require any inert gas, a target pattern shape and line width cannot be attained upon exposing the resist in an inert gas environment. A desired oxygen concentration in exposure differs even among individual color resists such as a blur resist, a green resist, and a red resist. Especially detection of a reference mark for calibration requires high precision, but the reference mark is normally positioned on the edge of a substrate stage. Therefore, when the reference mark is detected while flowing an inert gas onto the resist, a detection error occurs in response to a change in refractive index due to factors associated with the inert gas.